Bronchial stents are being used to address various ailments that potentially otherwise may restrict the breathing airways. For example, stents are disposed in the airways of patients suffering from chronic obstructive pulmonary diseases (COPD) and in the esophagi of patients suffering from cancer. Furthermore, the use of stents is on the rise in an expanding range of medical applications. For example, stents are used to keep blood vessels open, they are inserted into ureters to maintain drainage from kidneys, and they are inserted into bile ducts in addressing pancreatic cancer and cholangiocarcinoma (bile-duct cancer). Stents provide comfort and enhance longevity in many medical conditions where no direct cure is available.
Though stents are excellent devices when properly deployed, improper installation with regard to the disposition of a stent relative to its host lumen, or improper sizing of a stent with regard to its dimensions relative to the lumen, can lead to tissue inflammation, tissue granulation, stent migration, and other problems. Once a stent is improperly installed, adjusting its disposition or removing it out of concern for an error in sizing may require an invasive procedure. Proper sizing and placement of a stent are therefore of importance upon first installation.
Beyond initial time periods after a stent placement procedure, the principal importance of stent length as a risk factor for restenosis is becoming apparent, particularly, for example, to interventional radiologists. Typical methods of sizing stents rely on visual estimations from angiograms. Practitioners in this area need devices and methods for determining appropriate stent lengths.
Though excessive length of an endoluminal revascularization device can lead to migration and restenosis, there are also important risk factors associated with vessel diameter. Many practitioners pay more care in determining appropriate stent length than stent diameter. Some physicians generally employ expandable stents that, if allowed to fully expand, are larger than the diameter of the host lumen. This practice can lead to tissue granulation and further vessel damage.
Unfortunately, methods of obtaining luminal dimensions have diverged based on inquiry. Physicians involved in interventional cardiology and interventional radiology in particular have been attempting to find ways to deal with occluded or stenotic coronary arteries, blood vessels, tubular conduits, and other body lumens. The vessel diameter and a frequency shift are often measured with electronic calipers utilizing imaging and Doppler modes, respectively, for the determination of the mean flow rate through a vessel. Practitioners interested in hemodynamics and vessel patency, which relate to fluid flow through a treated segment and may be affected by recurrent stenosis, use alternative tools to measure the diameters of lumens. Often, imaging tests such as CT Scans are used to assist with dimensional calculations. Few devices have been developed that allow for accurate in situ measurement of tissue for the purposes of evaluating vessel patencies and for determining optimal dimensions and positions for interventional prostheses such as stents.
Therefore, there is an existing need for devices and methods for accurately measuring stenosis topography and luminal dimensions so that appropriately dimensioned interventional prostheses may be appropriately placed and installed. There is a need for lumen measuring devices and methods for measuring internal dimensions of a lumen at determinable positions along the length of the lumen.